This invention relates to a clutch for use with a linear drive screw that will slip when run against a stop as at the end of the screw drive or when linear motion is prevented for any reason.
It is frequently necessary in power drive mechanical systems to limit the amount of travel of a machine element. A widely used method of establishing travel limits for a motor driven machine component is to use electrical limit switches. When the component is caused to travel to its desired limit, the limit switch is tripped open so as to open a circuit in a motor controller which causes the motor to be disconnected from the power lines. In compact mechanical devices it is often difficult to find space to locate limit switches. In any case, it takes time to install limit switches and to wire and connect electric circuits which are incidental to their use.
In some devices in which a machine component is driven until it is physically stopped by running against an abutment, the electrical motor is not deenergized even though its rotor or armature is blocked against rotation. In such cases, motors are used that are designed for tolerating heavy current flow that results from blocking the rotor. This method wastes electricity. Moreover, if the machine component is blocked against travel for a substantial period of time, the motor will continue to draw current and may overheat if it is not disconnected in some other way.
A variety of slip clutches have also been developed for limiting the amount of force that can be transmitted through a motor driven mechanical system if some movable component becomes blocked or the acceptable physical load on the system is exceeded. These prior art slip clutches are very complex as they usually contain a large number of parts such as links, screws, collars, springs, and so forth. Besides being expensive to manufacture and inventory, these prior art clutches are more likely to fail because of their complexity and sensitivity to proper adjustment.